To summarize my impression of Trump's line of reasoning from that interview, not that I agree with him:
1. America is in trouble.
2. Much of America's trouble comes from bad deals or lack of negotiation.
3. I am a great negotiator.
4. Tariffs are useful in several ways: tariffs for protection of favored domestic industries, low tariffs for revenue, and high tariffs for leverage in negotiations.
5. As President, I can use tariffs to negotiate good deals.
6. Therefore I can save America by tariffs and that makes the word tariff "the most beautiful word in the dictionary."